Geranylgeranyltransferase I (
GGTase-I) is responsible for the posttranslational lipidation of several signaling
proteins such as RhoA, Rac1, and Cdc42, which contribute to
tumor development and
metastasis. However, the role of
GGTase-I in the progression of human
glioma is largely unknown. Here, we provide the evidence that Rac1 mediates the effects of
GGTase-I on the proliferation and apoptosis in human
glioma cells. We found that
GGTase-I was abundantly expressed in human primary
glioma tissues. Inhibition or downregulation of
GGTase-I markedly decreased the proliferation of
glioma cells and induced their apoptosis, while overexpression of
GGTase-I promoted cell growth in vitro. Inactivation of
GGTase-I eliminated geranylgeranylation of RhoA and Rac1, prevented them from targeting to the plasma membrane, and inhibited Rac1 activity. Furthermore, overexpressing wild type or constitutively active Rac1 stimulated
glioma cell growth, similar to the effect of
GGTase-I overexpression. Importantly, overexpressing dominant-negative Rac1 or Rac1 with the prenylation site deleted or mutated abrogated
GGTase-I-induced proliferation in
glioma cells. These results confirm the view that geranylgeranylation is essential to the activity and localization of Rho family
proteins and suggest that Rac1 is required for
GGTase-I-mediated
glioma growth.